The aim of this proposal is to develop high-resolution magnetic nanoparticles for use in Quadruple Magnetic Sorting (QMS). QMS is a flow-through immunomagnetic separation system that can provide sensitive enrichment of circulating cancer cells in blood as well as other biological fluids. Optimal cellular separation by QMS requires immunomagnetic particles having high magnetic susceptibility, narrow particle size distribution and high density attachment sites for antibodies. Current commercial immunomagnetic beads are either too large, lack size uniformity, or have too low magnetic susceptibility. We will make the necessary improvements in the magnetic immunobeads using recent advances in nano-particle technology and evaluate their performance by enriching ovarian cancer cells from a complex population of cultured cells. In Specific Aim 1 we will synthesize and physically characterize monodisperse paramagnetic nanoparticles using sol-gel methods to encapsulate Fe nano-crystals. These nanoparticles will have uniform size distribution and shape, and possess a high weight percentage of iron (Milestone 1). In Specific Aim 2 we will use siloxane treatments and heterobifunctional coupling agents to create high-density attachment sites for antibodies and streptavidin (Milestone 2). The resulting particles will be analyzed for their particle field interaction parameter values which is a major determinant of the effectiveness of magnetic nanoparticles in cellular separation (Milestone 3). Finally in Specific Aim 3 we will evaluate our magnetic nanoparticles for immunomagnetic detection and separation of ovarian tumor cells by QMS. The human ovarian tetracarcinoma PA-1 tumor cells will be diluted into whole blood and subjected to QMS using antibodies against TAG-72, a surface-expressed protein present on ovarian cancer cells. Demonstrating the detection of tumor cells in whole blood cells will be taken as the proof of principal for this project. [unreadable] [unreadable] [unreadable]